We propose to study the relative roles of the renin-angiotensin-aldosterone system and the autonomic nervous system in the regulation of blood pressure in sodium replete and sodium depleted dogs, both normotensive and hypertensive. The studies will range from the electron probe microanalysis of the sodium-potassium activated adenosine triphosphatase in the renal tubule and the effect of the renin-angiotensin-aldosterone on its distribution to the study of renovascular hypertension induced in salt depleted animals.